Accelerator facilities for research purposes and for use in the industrial and medical fields are employed to accelerate particles to extremely high energies. For example, in modern heavy ion accelerators, ions are accelerated to energies of several hundred GeV. These high-energy ions produce secondary radiation, meaning charged particles and neutrons, when they interact with material. The energy spectrum of the neutrons generated ranges from 0.025 eV up to several hundred GeV since the maximum energy of the neutrons generated can have the same energy range as the primary ion radiation. For protection against radiation it is necessary to detect the neutrons generated in order to dimension radiation protection measures, specifically shields, in such a way that prescribed limits can be met. Since high-energy neutrons have a long average path length in material, they can penetrate even extremely strong shields. So it is necessary and of great importance—in particular with heavy-ion therapy installations—to measure and monitor the neutron intensity (environmental monitoring). For radiation protection monitoring, it is important to develop dosimeters to verify neutron radiation which can be employed in the entire energy range of neutron radiation, from the range of thermal neutrons (0.025 eV) up to energies of several hundred GeV.
Dosimeters used here have a main body made of a hydrogenous material which is substantially spherical. A detection element is located in the center of the main body which detects the incident radiation. In order to be able to detect neutron radiation with extremely high energy, a neutron converter is provided which comprises metal atoms. They convert the neutrons to be detected into decelerated neutrons which lie in a suitable energy range of 0.025 eV to 1 keV so that they can be registered by the detection element. To evaluate the detected radiation, the detection element must be expanded. It has turned out that the construction of conventional dosimeters is complex and consequently monitoring the environment is possible only at relatively high cost.